Microstructural adaptations of the subchondral bone are related to the mechanical axis deviation in end stage varus oa knees.

Recent studies highlighted the crucial contribution of subchondral bone to OA development. Yet, only limited data have been reported on the relation between alteration to cartilage morphology, structural properties of the subchondral bone plate (SBP) and underlying subchondral trabecular bone (STB). Furthermore, the relationship between the morphometry of the cartilage and bone in the tibial plateau and the OA-induced changes in the joint's mechanical axis remains unexplored. Therefore, a visualisation and quantification of cartilage and subchondral bone microstructure in the medial tibial plateau was performed. End stage knee-OA patients with varus alignment and scheduled for total knee arthroplasty (TKA) underwent preoperative fulllength radiography to measure the hip-knee-ankle angle (HKA) and the mechanical-axis deviation (MAD). 18 tibial plateaux were µ-CT scanned (20.1 µm/voxel). Cartilage thickness, SBP, and STB microarchitecture were quantified in 10 volumes of interest (VOIs) in each medial tibial plateau. Significant differences (p < 0.001) were found for cartilage thickness, SBP, and STB microarchitecture parameters among the VOIs. Closer to the mechanical axis, cartilage thickness was consistently smaller, while SBP thickness and STB bone volume fraction (BV/TV) were higher. Moreover, trabeculae were also more superior-inferiorly oriented, i.e. perpendicular to the transverse plane of the tibial plateau. As cartilage and subchondral bone changes reflect responses to local mechanical loading patterns in the joint, the results suggested that region-specific subchondral bone adaptations were related to the degree of varus deformity. More specifically, subchondral sclerosis appeared to be most pronounced closer to the mechanical axis of the knee.

Primary constrained-condylar-knee designs outperform posterior-stabilized and cruciate-retaining designs in high-grade varus osteoarthritic knees during short-term follow-up: a pilot study.

INTRODUCTION: High-grade varus osteoarthrosis (OA) is characterized by a pronounced intra-articular varus deformity and associated insufficiency of the lateral ligamentous complex. When performing a total knee arthroplasty (TKA) in such a knee, traditionally the alignment is restored to neutral, and the medial soft tissue structures are released to compensate for the lateral laxity and balance the joint. However, another option would be to leave the medial soft tissues untouched and accept the lateral laxity but to compensate for it using an ML-stabilized constrained-condylar knee (CCK) design. Our aim was to prove our hypothesis that such knees would demonstrate better clinical stability and better functionality as well as subjective outcome scores. MATERIALS AND METHODS: We searched our bicenter database of 912 primary TKAs (from 2016 to 2019) for primary TKA patients with a preoperative varus alignment of > 8°. After inclusion, 60 patients were divided into three groups by implant design: CCK (n = 21), posterior-stabilized (PS) (n = 20) and cruciate-retaining (CR) (n = 19). Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee Society Score (KSS), UCLA-activity score, ML instability scores and both radiographic and clinical data were compared between groups. RESULTS: ML stability was significantly better in CCK designs (86% grade 0) compared to CR (37% grade 0) (p = 0.004) but not PS (70% grade 0) designs. No grade II instability was present in CCK and PS implants compared to 16% of CR implants. KSS and UCLA-activity score were higher in CCK designs compared to PS (p = 0.027, p = 0.041) and CR designs (p < 0.001, p = 0.007). OKS and FJS were higher in CCK designs compared to CR (p = 0.025, p = 0.008) but not to PS. CONCLUSION: The use of a CCK design to compensate for the lateral laxity in high-grade varus OA knees allowed to refrain from a medial release. CCK designs displayed improved clinical stability and better functionality as well as subjective outcome scores compared to less-constrained designs.

The pre-diseased coronal alignment can be predicted from conventional radiographs taken of the varus arthritic knee.

INTRODUCTION: The concept of restoring the constitutional, pre-diseased alignment has gained lots of interest among knee surgeons. Previous attempts to use the contralateral limb to bridge the gap between the arthritic and the constitutional alignment were unsuccessful. We investigated the usability of a mathematical formula to predict the constitutional (pre-diseased) coronal alignment once arthritis has occurred. It is our hypothesis that by using the KL grade, CPAK classification and four radiographic measurements of the arthritic knee, the pre-diseased coronal alignment could be predicted. MATERIAL AND METHODS: Hundred arthritic patients with consecutive X-rays were used to determine a mathematical formula. Five alignment parameters were determined on full-length X-rays: HKA angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA) and the tibial joint line angle (TJLA). A refinement of the algorithm was implemented based on a reference cohort, consisted of 250 young adults aged between 20 and 27 years. Moreover, all knees were subdivided based on their CPAK-phenotype and the Kellgren-Lawrence scale (KL scale). An independent arthritic cohort of 289 patients scheduled for primary total knee arthroplasty was included to verify the accuracy of the predicted HKAs (HKAPRED). RESULTS: In CPAK type 1, the HKAPRED was 3.86° varus (STD 1.39) and the HKAYHA was 4.0° varus. In CPAK type 2, the HKAPRED was 1.68° varus (STD 1.95) compared to a HKAYHA of 1.34° (STD 0.81). The average constitutional HKA is not different in both CPAK 1 (p = 0.61) and CPAK 2 (p = 0.25), and the difference in the mean is estimated to be equal to - 0.14 (95CI - 0.68 to 0.40) in CPAK 1 and 0.35 (95CI - 0.06 to 0.75) in CPAK 2. CONCLUSION: Using the KL grade, CPAK classification and four radiographic measurements of the arthritic knee, the pre-diseased coronal alignment can be predicted in 80% of the varus knees with an accuracy of ≤ 0.5°. The predicted HKA (HKAPRED) can be very useful in the current and future clinical practice.

Outcome of lateral retinacular nerve transection combined with release for recalcitrant iliotibial band friction syndrome.

In this retrospective study, a technique consisting in neurolysis of the lateral retinacular nerve combined with a partial release through elliptic excision of the iliotibial band (ITB) is evaluated for efficacy in recalcitrant ITB friction syndrome and compared with results from other techniques reported in literature. From April 2014 to December 2017, 21 patients suffering from recalcitrant ITB friction syndrome were surgically treated with the aforementioned technique. 15 patients (15 knees) were available for a written retrospective reassessment after completion of a follow-up period of at least 12 months. Residual pain was scored using the Visual Analogue Scale (VAS). The functional outcome was evaluated by two patient reported outcome measurement scales (PROMs), the Lysholm and the International Knee Documentation Committee (IKDC) score. Return to sport was analysed by duration of the inactivity period as well as by the Tegner score. Overall satisfaction was evaluated using a modified Boyden scale. At final follow-up of one year, the performed intervention resulted in a pain reduction (VAS 4.2 (1-8) to 1.4 (0-6)) and improved knee function (Lysholm 59.53 to 87.73, IKDC 75) with return to sport (Tegner 4.3 to 5.4) after a median of 23.8 weeks (6 to 52). Twelve patients reported good or excellent results (80%) at final follow-up, and 12 patients (80%) would undergo surgery again, if necessary. The treatment of recalcitrant ITB friction syndrome by combining neurectomy of the lateral retinacular nerve with elliptic excision of the ITB resulted in good to excellent results in 80% of treated cases with return to sport in 93%.

Operative management of isolated posterior cruciate ligament injuries improves stability and reduces the incidence of secondary osteoarthritis: a systematic review.

PURPOSE: To evaluate the evidence for operative and non-operative management of isolated posterior cruciate ligament (PCL) injuries. METHODS: Using Pubmed, EMBASE and Cochrane databases, a systematic review was conducted of studies investigating the treatment of isolated PCL injuries published until July 2020. Quality assessment was performed with the Cochrane risk of bias tool (level I), the Newcastle-Ottowa Scale (level II-III) and the National Institute of Health quality assessment tool (level IV). Clinical outcome measures included residual laxity, return to sports, patient-reported outcome measures, subsequent articular degeneration and complications. RESULTS: Twenty-seven studies [23 case series, 2 case-control, 1 cohort study and 1 randomized controlled trial (RCT)] including 5197 patients (5199 knees) with a mean age of 29.5 ± 3.6 years (range 15-68) fulfilled the study requirements. Significantly less residual laxity was found after posterior cruciate ligament reconstruction (PCLR) compared to non-operative management (3.43 vs. 5.47 mm, CI: 1.84-2.23, p < 0.001). Both treatment modalities yielded satisfying functional outcomes and a high return to sports (64-77%, mean: 70.3, CI: 67.8-72.2). Osteoarthritis (OA) occurred less frequently following PCLR (21.5 vs. 44.1%, p < 0.001). CONCLUSION: In the absence of level I RCTs, this systematic review suggests that surgical management for selected isolated PCL injuries is a reasonable option to consider, especially when the surgeon aims at minimizing residual laxity and presumably secondary osteoarthritis. LEVEL OF EVIDENCE: IV.

Knee joint laxity is restored in a bi-cruciate retaining TKA-design.

PURPOSE: The goal is to evaluate the passive stability of a bicruciate retaining, cruciate retaining and bicruciate substituting TKA design in relation to the native knee stability in terms of the laxity envelope. A bicruciate retaining knee prosthesis was hypothesized to offer a closer to normal knee stability in vitro. METHODS: Fourteen cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque, distraction/compression force and an anteroposterior shear force. Subsequently, the native knee, bicruciate retaining, cruciate retaining and finally a bicruciate substituting total knee arthroplasty were tested. RESULTS: Through the range of motion, the width of the varus/valgus and internal/external laxity envelope for the native knee and the bicruciate retaining knee were almost equivalent, whereas the cruciate retaining and the bicruciate substituting knee displayed less laxity and more joint distraction. In all prosthetic knees, an equal anteroposterior laxity was seen for the lateral and medial side whereas in the native knee, a difference in laxity was seen between the stable medial side and the more mobile lateral side. CONCLUSION: Bicruciate retaining knee prostheses can restore normal laxity and thus have the potential to offer more normal knee function. Restoration of natural peri-articular soft-tissue tension is clinically important because of its obvious effects on joint stability and range of motion. Furthermore, the results of this study could help to establish the ideal ligament tension and laxity in more conventional implants by approaching the normal values for passive knee evaluation as presented here.

A revisited technique for combined anterior cruciate ligament and anterolateral ligament reconstructions.

A new technique for combined anterior cruciate ligament and anterolateral ligament reconstructions is described. An iliotibial band strip is used as an ALL graft , leaving the distal insertion intact and fix it with a knotless anchor on the femoral origin, after tunneling it under the lateral collateral ligament.

High risk of tunnel convergence during combined anterior cruciate ligament and anterolateral ligament reconstruction.

PURPOSE: To assess the risk of femoral tunnel convergence in combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstructions. The hypothesis was that a more proximal and anterior orientation of the ALL femoral tunnel should reduce the risk of convergence with the ACL femoral tunnel. METHODS: 15 fresh-frozen cadaver knees were examined. An anatomic ACL femoral tunnel was drilled arthroscopically in each specimen and ALL tunnels were made in two directions: (1) 0° coronal angulation and 20° axial angulation, (2) 30° coronal angulation and 30° axial angulation. Computed tomography scans were performed to investigate tunnel convergence and to measure the minimal distance between tunnels, tunnel length and the LFC width. RESULTS: Tunnel convergence occurred in 20 of 30 cases (67%). Convergence was significantly reduced when tunnels were drilled at 30° coronal and 30° axial angulation (p < 0.05). The mean length of the ALL tunnel was 15.9 mm [95% CI (13.6; 18.1)] and was independent of ALL tunnel angulation. The mean minimal distance between the ALL and ACL tunnel was 3.1 mm [95% CI (2.1; 4.1)]. The odds ratio for tunnel convergence was 3.5 for small LFC, relative to large LFC (n.s.) CONCLUSION: A high risk of tunnel convergence was observed when performing combined ACL and ALL reconstructions. The clinical relevance of this work is that the occurrence of tunnel conflicts can be reduced by aiming the ALL tunnel in a more proximal and anterior direction. Surgeons should be aware of this, since tunnel convergence could jeopardize the ACL reconstruction and fixation.

The shape and orientation of the trochlea run more parallel to the posterior condylar line than generally believed.

PURPOSE: This study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur. METHODS: The rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis. RESULTS: The anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (p = 0.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2 mm (SD 1.8 mm). CONCLUSION: The ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2 mm when the femoral component is externally rotated. LEVEL OF EVIDENCE: III.

Principal component analysis as a tool for determining optimal tibial baseplate geometry in modern TKA design.

Optimal tibial component fixation in total knee arthroplasty (TKA) requires maximal tibial bone coverage, optimized mediolateral cortical fit as well as component rotation. Failure to achieve an optimal fit may result in component subsidence and loosening in case of undersizing, or overhang with subsequent soft tissue impingement in case of overhang. To date there is no consensus on optimal tibial component shape, and significant variability exists among different design manufacturers. In this study "principal component analysis" was used as a statistical tool in order to determine the ideal tibia baseplate shape, based upon anthropometric CT- scan data defining an average proximal tibial shape and variations. Gender specificity was evaluated and differences in geometry depending on anatomic constitution (varus, neutral, valgus) were analyzed. The results from our study indicate that in the arthritic knee differences in proximal tibial morphology at the resection level were mainly attributed to size and not shape. This is true for both Caucasian men and women, and is independent from the anatomical constitution.

Predictors of outcome after manipulation under anaesthesia in patients with a stiff total knee arthroplasty.

PURPOSE: Flexion in a stiff total knee arthroplasty (TKA) can be improved by manipulation under anaesthesia (MUA). Although this intervention usually results in an improvement in range of motion, the expected result is not always achieved. The purpose of this study is to determine which factors affect range of motion after manipulation in patients with a stiff total knee. METHODS: After exclusion (n = 22), the data of 158 patients (138 knees) with a stiff knee after TKA who received a manipulation under anaesthesia between 2004 and 2014 were retrospectively analysed. Pre-, peri- and post-operative variables were identified and examined for their influence on flexion after the manipulation using Kruskal-Wallis and Mann-Whitney U tests and Spearman correlations. RESULTS: After MUA, a mean improvement in flexion of 30.3° was observed at the final follow-up. Preoperative TKA flexion, design of TKA and interval between TKA procedure and MUA were positive associated with an increase in flexion after MUA. MUA performed 12 weeks or more after TKA procedure deteriorated the outcome. CONCLUSIONS: Three factors, pre-TKA flexion type of prosthesis and interval between TKA procedure and manipulation under anaesthesia, were found to have impact on flexion after TKA and MUA were identified. Results are expected to be inferior in patients with low flexion before TKA procedure or with a long interval (>12 weeks) between the TKA procedure and the manipulation under anaesthesia. LEVEL OF EVIDENCE: IV.

Bone morphotypes of the varus and valgus knee.

BACKGROUND: Coronal deformity correction with total knee arthroplasty (TKA) is an important feature in the treatment of osteoarthritis (OA). The hypothesis of this study was that bone morphology would be different in varus and valgus deformity, both before osteoarthritis development as well as during and after the disease process of OA. MATERIALS AND METHODS: Retrospective study with measurements on preoperative and postoperative full leg standing radiographs of 96 patients who underwent TKA. The included patients were selected for this study because they had an OA knee on one side and a non-arthritic knee on the contralateral side presenting the same type of alignment as the to-be-operated knee (varus or valgus alignment on both sides). The control group of 46 subjects was a group of patients with neutral mechanical alignment who presented for ligamentous problems. A single observer measured mechanical alignment, anatomical alignment, anatomical-mechanical femoral angle and intra-articular bone morphology parameters with an accuracy of 1°. RESULTS: Varus OA group has less distal femoral valgus (mLDFA 89°) than control group (87°) and valgus OA group (mLDFA 85°). Varus OA group has same varus obliquity as control group (MPTA 87°) but more than valgus OA group (MPTA 90°). Joint Line Congruency Angle (JLCA) is 3°open on lateral side in varus and medially open in valgus OA group (2°). The non-arthritic valgus group presents a constitutional mechanical valgus of 184° Hip-Knee-Ankle (HKA) angle. DISCUSSION: Varus deformity in OA as measured with an HKA angle (HKA) <177° is a combination of distal femoral wear, tibial varus obliquity and lateral joint line opening. Valgus deformity in OA with an HKA > 183° is a combination of femoral distal joint line obliquity and wear combined with medial opening due to medial collateral ligament stretching. The clinical importance of bone morphotype analysis is that it shows the intra-articular potential of alignment correction when mechanical axis cuts are performed. CONCLUSION: Bone morphology in varus and valgus deformity is different before and after osteoarthritis. Perpendicular cuts to mechanical axes do not necessarily lead to neutral mechanical axis. Constitutional mechanical valgus was observed as 184° HKA angle before the development of OA. LEVEL OF EVIDENCE: Level IV study.

Mean tensile strength of the PCL in TKA depends on the preservation of the tibial insertion site.

PURPOSE: The tibial insertion of the posterior cruciate ligament (PCL) frequently becomes damaged when performing a tibial cut in a PCL-retaining total knee replacement (TKA). The aim of this study was to quantify the functional effect of this structural damage on the tensile strength and failure load. METHODS: Six paired knees from fresh-frozen cadaver specimens were used. All soft tissues but the PCL were removed. In the left-sided specimens, a classic tibial cut at a depth of 9 mm with 3° of posterior slope was made, while in the right-sided specimens, a bone block was left in front of the tibial PCL insertion. After cementing a tibial tray, the specimens were mounted in a loading frame in 60° of flexion. The femur was translated anteriorly at a constant velocity rate of 0.5 mm/s. Tensions in the PCL were measured continuously until failure occurred. RESULTS: In one specimen, the tibial PCL insertion was completely removed by the tibial cut. In the other five paired specimens, the mean tensile strength of the PCL was 380.6 ± 154.7 N in the left-sided knees. In the right-sided knees, the mean tensile strength was 738.4 ± 166.7. The average right-to-left ratio was 2.2 ± 0.7 (p = 0.006). CONCLUSION: The results of this study indicate that the conventional technique for tibial preparation in cruciate-retaining total knee arthroplasty can result in a significant decrease in tensile strength of the PCL, rendering it susceptible to failure and subsequent midflexion instability. Therefore, we recommend leaving the posterior tibial cortex anterior to the PCL insertion intact when performing a cruciate-retaining TKA.

Should we aim at undercorrection when doing a total knee arthroplasty?

PURPOSE: Restoration of neutral mechanical alignment is traditionally considered as one of the prerequisites for successful total knee replacement. The purpose of this study was to investigate whether a certain bias towards undercorrection exists with conventional total knee arthroplasty (TKA) instruments. METHODS: A cohort of 456 consecutive patients, who underwent the same standardised TKA with restoration of neutral mechanical alignment as target, was studied. Based on the preoperative alignment, patients were stratified into three categories: valgus, neutral and varus. Component and limb alignment were compared between these groups. RESULTS: The mean post-operative hip-knee-ankle angle was -0.7° (SD 2.5) in valgus knees, 0.2° (SD 1.9) in neutral knees and 2.4° (SD 3.9) in varus knees (p < 0.001). About 39.8% of the varus knees remained in >3° of varus post-operative and 20.2% of the valgus knees remained in <-3° of valgus. A systematic unintentional undercorrection was noted in varus knees, which was proportional to the preoperative varus deformity and which was caused by varus positioning of both the femoral and tibial components. In valgus knees, the undercorrection was caused almost exclusively by valgus bias of the femoral component's position. CONCLUSION: This study showed that conventional TKA instruments are associated with a systematic unintentional bias towards undercorrection of the pre-existing deformity. The clinical relevance of this study is that intentionally aiming at slight undercorrection of the deformity may lead to excessive undercorrection in reality in case the surgeon does not recognise the automatic bias that already exists with standard instruments. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs.

PURPOSE: Posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs. METHODS: All prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras. RESULTS: The post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle. CONCLUSION: Post-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.

Current opinions about coronal plane alignment in total knee arthroplasty: A survey article.

PURPOSE: To survey an audience of international knee surgeons about their current opinions on the analysis of coronal knee alignment and their objectives for postoperative alignment in total knee arthroplasty. METHODS: Survey of 300 surgeons from 32 different countries with an audience response system allowing three possible answers being either a positive or negative answer or an abstention. RESULTS: Surveyed surgeons perform rarely preoperative and postoperative full leg radiographs and evaluate radiological outcomes more with short films. The main trend in this survey was towards neutral mechanical alignment, however varus alignment is acceptable in constitutional varus patients. This residual varus should be obtained through a femoral varus cut rather than a tibial varus cut. The valgus knee can remain in slight valgus but most of the correction will be performed at the femoral level. The main objective of postoperative alignment in TKA is a joint line parallel to the floor and a central load-bearing axis through the middle of the arthroplasty. Surgeons prefer unicompartmental arthroplasty more for themselves than for their patients in case of medial bone on bone arthritis. CONCLUSIONS: Neutral mechanical axis with a joint line parallel to the floor and a centrally running load bearing axis remains the central scope of the surveyed surgeons. Because of the literature on residual varus it becomes more acceptable for the orthopaedic community to accept this type of outlier before aiming at a surgical correction.

Injuries in male versus female soccer players: epidemiology of a nationwide study.

The aim of this study is to analyse soccer injuries on a national scale over one decade and to compare injury rates by gender. Detailed injury data obtained from the Royal Belgian Football Association from seasons 1999-2000 and 2009-2010 were recorded and gender differences in incidences of injuries, type of injury, affected body part and timing of injury were compared. A significant decrease in injuries from 7.56 to 5.96 injuries per 100 players was seen (p<0.0001). Overall male players sustained more cont usions, fractures, joint dislocations and musculotendinous injuries than female players. Proportionally, females sustained more severe injuries than men (p<0.0001). Significantly more injuries where sustained during competition in both males and females. The number of injuries in male and female soccer players has decreased over the past decade. A higher injury rate was seen in men but proportionally, females sustained more severe injuries.

The adductor ratio: a new tool for joint line reconstruction in revision TKA.

PURPOSE: In this study, the value of the adductor tubercle as landmark for joint line reconstruction in revision total knee arthroplasty (TKA) was investigated. METHODS: On 100 calibrated full-leg standing radiographs obtained from healthy volunteers, distances from the medial epicondyle, the lateral epicondyle, the adductor tubercle, the fibular head and the centre of the knee to the joint line were determined. RESULTS: The average distance to the joint line from the medial epicondyle, the lateral epicondyle, the adductor tubercle and the fibular head was found to be 27.7 mm (SD 3.0), 27.1 mm (SD 2.7), 44.6 mm (SD 4.3) and 15.1 mm (SD 3.7), respectively. The distance from the adductor tubercle (R = 0.82) and the centre of the knee (R = 0.86) to the joint line showed a strong and linear correlation with the femoral width. The medial epicondyle, the lateral epicondyle and the fibular head showed less strong correlations. There was no significant correlation with the limb alignment. The adductor ratio was defined as the distance from adductor tubercle to the joint line divided by the femoral width and was found to be 0.52 (SD 0.027) with only small inter-individual variation. The adductor ratio was the most accurate ratio and reconstructed the joint line within 4 mm of its original level in 92% of the cases. CONCLUSION: The adductor ratio is a reliable and accurate tool for joint line reconstruction in revision TKA. It was found to be more accurate then the use of absolute distances and the epicondylar ratios. This study supports the use of the adductor tubercle for joint line reconstruction in revision TKA. LEVEL OF EVIDENCE: II.

Anatomic single-bundle ACL surgery: consequences of tibial tunnel diameter and drill-guide angle on tibial footprint coverage.

PURPOSE: To investigate the consequences of differences in drill-guide angle and tibial tunnel diameter on the amount of tibial anatomical anterior cruciate ligament (ACL) footprint coverage and the risk of overhang of the tibial tunnel aperture over the edges of the native tibial ACL footprint. METHODS: Twenty fresh-frozen adult human knee specimens with a median age of 46 years were used for this study. Digital templates mimicking the ellipsoid aperture of tibial tunnels with a different drill-guide angle and a different diameter were designed. The centres of these templates were positioned over the geometric centre of the tibial ACL footprint. The amount of tibial ACL footprint coverage and overhang was calculated. Risk factors for overhang were determined. Footprint coverage and the risk of overhang were also compared between a lateral tibial tunnel and a classic antero-medial tibial tunnel. RESULTS: A larger tibial tunnel diameter and a smaller drill-guide angle both will create significant more footprint coverage and overhang. In 45% of the knees, an overhang was created with a 10-mm diameter tibial tunnel with drill-guide angle 45°. Furthermore, a lateral tibial tunnel was found not to be at increased risk of overhang. CONCLUSION: A larger tibial tunnel diameter and a smaller drill-guide angle both will increase the amount of footprint coverage. Inversely, larger tibial tunnel diameters and smaller drill-guide angles will increase the risk of overhang of the tibial tunnel aperture over the edges of the native tibial ACL footprint. A lateral tibial tunnel does not increase the risk of overhang.

Can a tibial tunnel in ACL surgery be placed anatomically without impinging on the femoral notch? A risk factor analysis.

PURPOSE: To analyze anatomical risk factors and surgical technique dependent variables, which determine the risk for femoral notch impingement in anatomically correct placed tibial tunnels for anterior cruciate ligament (ACL) surgery. METHODS: Twenty fresh frozen adult human knee specimens under the age of 65 years were used. Digital templates mimicking a tibial tunnel aperture at the tibia plateau were designed for different tibial tunnel diameters and different drill-guide angles. The centres of these templates were placed over the geometric centre of the native tibial ACL footprint. The distances between the anterior borders of the templates and the anterior borders of the footprints (graft free zone) were measured and compared. Furthermore, anatomic risk factors for femoral notch impingement were determined. RESULTS: The graft free zone was statistically significantly longer for larger drill-guide angles compared to smaller drill-guide angles (p < 0.00001). Furthermore, 8 mm diameter tibial tunnels had a statistically significant larger graft free zone compared to 10-mm-diameter tibial tunnels (p < 0.00001). For the 10 mm diameter tibial tunnels with drill-guide angle of 45°, 9 out of 20 knees (45 %) were "at risk" for notching and 4 out of 20 knees (20 %) had "definite" notching. For 10-mm tunnels with drill-guide angle of 45°, a risk for notching was associated with smaller tibial ACL footprint (p < 0.05). CONCLUSION: If a perfect centrally positioned tibial tunnel is drilled, a real risk for femoral notch impingement exists depending on the size of the tibial ACL footprint and surgery-related factors. Therefore, in anatomical tibial tunnel placement in single bundle ACL reconstruction surgery, particular attention should be paid to size of the tunnel and drill-guide angle to minimize the risk of femoral notch impingement.